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ISQL plan output is unexpectedly truncated after a query is simplified to become shorter [CORE5061] #5348

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firebird-issue-importer opened this issue Dec 31, 2015 · 5 comments

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@firebird-issue-importer

Submitted by: @pavel-zotov

Attachments:
isql-explained-plan-cut-off-when-query-is-simlified.zip

Consider two queries from attached zip. The only difference between them is:

Q1:
select
char_length(mon$explained_plan)
,(select count(*) from r4)
,(select count(*) from rn)
,(select count(*) from rn)
from mon$statements

Q2:
select
char_length(mon$explained_plan)
,(select count(*) from r4)
,(select count(*) from rn)
--,(select count(*) from rn)
from mon$statements

(i.e. Q2 is simplified: one of columns is excluded from selection).

Q1 has length of mon$explained plan = 64436 and length of ouput in ISQL when "set explain on" = 64944 (difference ~500 can be explained by number of occurences ascii_char(13) in output of 'set explain on').

Q2 (which is **simplified** case of Q1) has length of mon$explained plan = 63237 but length of ouput in ISQL when "set explain on" = 33024. Plan in ISQL looks as:

                                        \-\>  Nested Loop Join \(anti\)
                                            \-\> Recursion
                                                \-\> First N Records
                                                    \-\> Window
                                                        \-\> Record Buffer \(record length: \.\.\.

===

Checked on WI-V3.0.0.32256.

Commits: 24b7a79 FirebirdSQL/fbt-repository@f60a6b7

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firebird-issue-importer commented Dec 31, 2015

Modified by: @pavel-zotov

Attachment: isql-explained-plan-cut-off-when-query-is-simlified.zip [ 12864 ]

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firebird-issue-importer commented Jan 2, 2016

Modified by: @dyemanov

assignee: Dmitry Yemanov [ dimitr ]

summary: ISQL output of explained plan is shorter by ~ 2 times when query is simplified by removing one of selected columns from it => ISQL plan output is unexpectedly truncated after a query is simplified to become shorter

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firebird-issue-importer commented Jan 2, 2016

Modified by: @dyemanov

status: Open [ 1 ] => Resolved [ 5 ]

resolution: Fixed [ 1 ]

Fix Version: 3.0 RC2 [ 10048 ]

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firebird-issue-importer commented Jan 5, 2016

Modified by: @pavel-zotov

status: Resolved [ 5 ] => Resolved [ 5 ]

QA Status: No test => Done successfully

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firebird-issue-importer commented Jan 5, 2016

Modified by: @pavel-zotov

status: Resolved [ 5 ] => Closed [ 6 ]

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